Introduction to Symmetric and Asymmetric Encryption

Do you know how the online security cryptosystem works to keep messages transmitted over the Internet safe?

There are 2 main methods to encrypt messages via the Internet: (1) Symmetric key cryptosystem and (2) Asymmetric key cryptosystem.

Symmetric Encryption

Symmetric key cryptosystem uses an identical private key to encrypt and decrypt messages. The private key consists of numbers, words and billions of character strings. In this cryptosystem, both a message sender and a message receiver shares an identical private key for encryption and decryption. Note that once a private key is stolen or unintentionally disclosed, anyone can decrypt the encrypted message.

Asymmetric Encryption

A much more secure cryptosystem is the asymmetric key cryptosystem and was invented in the 1970s. Asymmetric key cryptosystem requires a pair of keys: a public key and a private key for encryption and decryption.

In this cryptosystem, a message sender needs to get a public key from a message receiver and then encrypt the message by using the given key. Message receiver decrypts the message by using a corresponding private key which only the message receiver has. In an asymmetric key cryptosystem, the key for encryption (public key) and the key for decryption (private key) are completely non-identical to assure high security for the message.

Symmetric & Asymmetric Encryption Application

SSL Certificates use the key cryptosystem, a public key for encryption and a private key for decryption.

Take an online retailer’s website secured by an SSL Certificate for instance.

1) Buyer’s web browser encrypts the common key by using the public key stored in online retailer’s SSL certificate and sends the common key to the online retailer.

2) Online retailer’s web server decrypts the received message by using the private key that is corresponding to the public key and receives the common key sent by the buyer.

Even if a third party monitors the ordering data in transmission, he/she cannot read the data because they do not have a private key for decryption.

About us

Cyber Secure Asia (CSA) is an official partner of DigiCert, a US-based Certificate Authority (CA) providing and specializing in SSL certificates and management tools in the Asian region. If you’d like to know more on SSL certificates, contact us for details.